JP2010509877A - Method for establishing a bidirectional data transmission path in a mesh wireless communication network - Google Patents

Abstract

In a method for establishing a bidirectional data transmission path in a wireless meshed packet-switched communication network, a logical topology in the form of at least one routing tree can be proactively established, wherein a root network node of the routing tree sends first unidirectional data transmission paths regarding routing request messages specifying the root network node to the network nodes of the communication network in periodic time intervals. A first flag is provided in the network nodes of the routing tree that can be put into two different states. Upon receipt of a routing request message, a network node only sends a second unidirectional data transfer path regarding the routing response message specifying the network node to the root-network node if the first flag is switched into a first selectable state. Thus, a bidirectional data transfer path between the root network node and the network node is established.

Description

  The present invention belongs to the field of communication technology and relates to a method for establishing a bidirectional data transmission path in a mesh wireless communication network.

  The invention also relates to a mesh wireless communication network suitable for performing the method.

From the wireless WLAN network (WLAN = W ireless L ocal A rea N etwork) In the early 1990s, the Institute of Electrical and Electronics Engineers (IEEE) in the framework of standards group IEEE 802.11, have been published many various standards In these standards, specific characteristics of communication networks are defined with binding power based on rapidly developing technology development, for example, transmission rate, frequency domain, modulation method, number of channels and encryption are binding power. It is prescribed with.

  In such a conventional standard, the minimum unit of a WLAN communication system is a wireless cell in which an access point can exchange data with a plurality of terminal devices. In order to connect a plurality of wireless cells to each other, a cable connection between access points is used.

  The latest development within the standard group IEEE 802.11, also referred to as IEEE 802.11s, which will be published as an effective standard in 2009, standardizes wireless communication between network nodes. In IEEE 802.11s, a network node that is a so-called mesh point, abbreviated as MP (MP = Mesh Point), is used as a router for wireless data transmission. Thereby, a mesh-type wireless ad hoc wireless network (mesh network) is formed.

  In general, a proactive, reactive or hybrid routing protocol can be implemented in a communication network.

  In a communication network using a proactive routing protocol, a data transmission path between a source node and a target node is already provided at the time of data transmission, so that a quick data exchange can be performed, but in particular, resources are reserved. Therefore, there is a disadvantage that it cannot be used for data exchange. In the case of the reactive routing protocol, the data transmission path between the source node and the target node is established only when requested. This is relatively advantageous in terms of resources, but leads to a latency time when forming a data transmission path.

In order to take advantage of the proactive routing protocol and the reactive routing protocol, HWMP (HWMP) is used to select a data transmission path between a source node and a target node for a wireless communication network conforming to the IEEE 802.11s standard. = H ybrid W ireless M esh P rotocol) hybrid routing protocol named are provided. In HWMP, a logical topology in the form of one or more routing trees can be established on the physical topology of the network. In order to establish and update the routing tree, the root MP sends a routing inquiry message to other MPs in a broadcast manner at periodic time intervals. This routing inquiry message "proactive route request", for short called proactive PREQ (PREQ = P ath Req uest ). The MP receives the PREQ, and inputs the corresponding route data into the routing table, thereby forming a unidirectional data transmission route from the MP to the route MP on the transmission side. In order to keep the number of routing messages for forming the local routing tree as small as possible, the so-called proactive PREP flag for the routing response message PREP (PREP = Path Reply) can be cleared in the proactive PREQ. That is, the MP receives the proactive PREQ and forms a forward path for data transmission from the MP to the root MP, but does not transmit a routing response message (PREP) to the root MP, so that data transmission from the root MP to the MP is performed. The return path for is not established.

  Since the data flow between the root MP and MP in the routing tree is often bi-directional, in HWMP, at the start of data communication, ie before the first data packet is still sent from the MP to the root MP. By transmitting a routing response message (PREP) from the MP to the root MP, a unidirectional return path can be established from the root MP to the MP that transmits the PREP.

  The unidirectional data transmission path (outward path) from the MP to the root MP is periodically updated by the PREQ periodically transmitted from the root MP, so that the unidirectional forward path of the routing tree is changed in the mesh network. Can adapt to changing conditions. In particular, MPs newly added to the mesh network can be incorporated into the routing tree, or the data transmission path that has become incapable of functioning due to, for example, a missing data link can be changed.

However, the return path from the root MP to the MP is not updated and is maintained in the same way as when established by sending a PREP from one MP before sending the first data packet of data communication, so that the connection is When the link metrics change without change, the forward path and the return path between the root MPs are different, and the data packet takes a more advantageous path on the forward path (updated), and on the return path (unupdated) A) which is relatively unfavorable. When a data link is lost in the data transmission path between the root MP and the MP, an alternative forward path is established between the root MP and the MP by the periodically transmitted PREQ, whereas the return path is not updated. Data transmission cannot be performed above. In this case, standard mechanism based upon the HWMP AODV (AODV = A d hoc O n demand D istance V ector) is used. This leads to a relatively long latency time until the start of data packet transmission from the root MP to the MP.

  On the other hand, an object of the present invention is to provide a method for avoiding the above-mentioned drawbacks in a method for establishing a bidirectional data transmission path in a mesh type wireless communication network.

  According to the present invention, the object is solved by a method for establishing a bidirectional data transmission path in a mesh type wireless communication network having the configuration of claim 1. Advantageous embodiments of the invention are listed as features of the dependent claims.

  According to the present invention, there is provided a method for establishing a bidirectional data transmission path in a mesh type wireless packet switched (ad hoc) communication network, wherein at least one tree shape is formed on a physical topology of the bidirectional data transmission path. It provides a way in which a logical topology having a structure ("routing tree") is or has been established proactively. To do this, in order to establish the first unidirectional data transmission path to the network node of the communication network that is used in the routing tree as the root network node, the root network node is in a periodic time interval at the RAN. A routing inquiry message abbreviated as (RAN = Routing-Anfrage-Nachricht) is generated and transmitted to the network node of the communication network. For this purpose, when the network node receives the RAN, the target network node is compared with the target network node (root network node) in the routing table (forwarding table) of the network node of the communication network that receives the RAN. Add or update an entry that includes the path metrics to and the next hop (ie, the next network node on the path to the target network node that is the network node that received the RAN). Further, for example, the hop count can be stored in the routing table. The method for establishing the routing tree can be based, inter alia, on procedures implemented in the hybrid routing protocol HWMP. In particular, the routing inquiry message (RAN) can be a proactive route request (PREQ) according to the hybrid routing protocol HWMP.

In the network node of the routing tree, a first flag is set that can transition to two different states in order to control the transmission of the routing response message. If the first flag of the network node of the routing tree is transitioned to a selectable first state, when this network node receives a routing inquiry message (RAN) from the root network node, the RWN (RWN = R outing A routing response message, abbreviated as A ntwort- N achricht), is transmitted to the root network node via the network node included in the first unidirectional data transmission path. If the first flag of the network node of the routing tree is shifted to the second state, the network node does not generate an RWN when it receives a RAN from the root network node. With such an RWN, a second unidirectional data transmission path from the root network node to the network node that generates the RWN is set. Further, when the RWN is received by the network node, the path metric and the next hop (that is, the RWN) on the route to the network node that generated the RWN are sent to the network node that generated the RWN in the routing table (forwarding table). And the next network node on the path to the network node that generated the receiving RWN) can be added or updated. Furthermore, the hop count can be stored in the routing table. In particular, the routing response message (RWN) can be a route response (PREP) according to the hybrid routing protocol HWMP. The root network node receives this routing response message (RWN) and establishes a second unidirectional data transmission path from the root network node to the network node that generated the RWN. As a result, a bidirectional data transmission path is established between the root network node and the network node that generated the RWN.

  In the communication network, data packets are transmitted from one network node to another network node in the same layer (OSI model). This layer is in particular the second or third layer.

  The method according to the invention advantageously establishes a bidirectional data transmission path between the root network node and the network node of the routing tree only if the data packet is actually transported on the data transmission path. This results in a relatively small number of routing messages. Furthermore, in addition to the forward path from the network node to the root network node, the return path from the root network node to the network node is also updated to update the data packet between the root network node and the network node. Be able to use bi-directional data transmission paths and respond quickly to changes in data transmission paths, whether data transmission paths change due to path metrics changes or data transmission paths change due to missing data links To.

  The first flag is, for example, “set” in the first state, that is, “on” or “1”, and “erased” in the second state. That is, it is set to the “off” state or “0”. Further, the first flag can be set to the “off” state in the first state, and can be set to the “on” state in the second state.

  In an advantageous embodiment of the method according to the invention, the network node of the routing tree is the root network node (“target network node”) as the first network node of the communication network (“source network node”) on the data transmission path to the root network node. When a data packet to be transmitted to the node “)” is received, the first flag of the network node is shifted to the first state. In this case, this network node receives the data packet from a layer (OSI model) higher than the layer in which the data packet is transmitted in the communication network. This makes it particularly easy to establish a bidirectional data transmission path from the root network node to the network node when requested.

  In another advantageous embodiment of the method according to the invention, the first flag of the network node is moved to the second state immediately after the routing response message (RWN) is sent to the root network node. This has the advantage of corresponding to a routing protocol sequence. In addition, no timer is required.

  In another advantageous embodiment of the method of the invention, a data packet transmitted by a network node as a source network node (the network node received as the first network node of the communication network on the data transmission path to the root network node) Only after the elapse of a first selectable period starting at the same time as the packet) is transmitted to the target network node, the root network node, the first flag of the network node is shifted to the second state. This first period is reset to a selectable period start value each time a data packet is transmitted in which the network node is the source network node and the root network node is the target network node. Such an embodiment of the method according to the invention can be implemented particularly simply.

  In another advantageous embodiment of the method according to the invention, the network node is transmitted to the root network node as the source network node (the network node as the first network node of the communication network on the data transmission path to the root network node) If the data packet is received as a source network node for a certain second period of time immediately before receiving the data packet (ie, the root network that is the first network node of the communication network) A data packet for transmission to a node is not received as the first network node of the communication network on the data transmission path to the root network node), the network node sends a routing response message RWN) is generated and transmitted to the root network node. This advantageously allows a bi-directional data transmission path to be established between the root network node and the network node each time data communication starts.

  In particular, in the above-mentioned last embodiment of the method according to the invention, the second flag that can be transitioned to and set in two different states at the network node has been transitioned to a selectable second state. In some cases, the network node can generate and send a routing response message (RWN) to the root network node. This makes it possible to carry out the method according to the invention in a particularly simple manner.

  The second flag is, for example, “set” in the first state, that is, “on” or “1”, and “erased” in the second state. That is, it is set to the “off” state or “0”. Further, the second flag can be set to the “off” state in the first state, and can be set to the “on” state in the second state.

  In another embodiment of the method according to the invention, if the data packet is the first data packet of the data communication, the network node sends a routing response message (RWN) before the first data packet (D1) of the data communication. When transmitted to a node, the first flag of the network node can be shifted to the first state. The fact that this data packet is the first data packet of data communication can be identified, for example, by the second flag being shifted to the second state. However, this adds a condition that must be queried.

  In another embodiment of the method according to the invention, a routing response message (RWN) is sent immediately after a routing inquiry message (RAN) is received at the root network node. In an alternative embodiment of the method of the invention for this embodiment, a routing response message (RWN) is transmitted with a time delay after a routing inquiry message (RAN) is received at the root network node (R). . In the present invention, the latter alternative embodiment is advantageous. This is because this embodiment has the advantage that the number of routing messages can be reduced because the probability of receiving another routing inquiry message (RAN) with better path metrics after receiving the RWN is reduced.

  In another advantageous embodiment of the method according to the invention, the lifetime parameter of the routing response message (RWN), which indicates the lifetime of the second unidirectional data transmission path to the network node, is the received routing query. The following lifetime parameter included in the message (RAN), that is, the lifetime parameter for indicating the lifetime of the first unidirectional data transmission path to the route network node (R) is set. This advantageously makes it possible to equalize the round trip lifetimes of the bidirectional data transmission path between the root network node and the network node.

  The present invention further relates to a method for establishing a bidirectional data transmission path in a mesh type wireless packet switching communication network as described above, and more particularly to a method that can be combined with the above method. In this method, when a change in the first unidirectional data transmission path to the root network node is detected when the first flag is shifted to the selectable first state, the second to the network node is detected. By sending a routing response message (RWN) designating a unidirectional data transmission path to the root network node, a bidirectional data transmission path is established between the root network node and the network node.

  The present invention further extends to the mesh wireless packet switched (ad hoc) communication network configured to implement the method.

  Furthermore, the present invention extends to a network node of the mesh-type wireless packet switched (ad hoc) communication network in which the above machine-readable program code is executed.

  The present invention also extends to a storage medium storing the above-described machine-readable program code.

  Hereinafter, the present invention will be described in detail based on examples. Here, reference is made to the accompanying drawings.

It is the schematic which shows one Example of the mesh type | mold wireless communication network of this invention with which the routing tree was established. FIG. 2 is a schematic diagram showing transfer of a data packet D1 as a source network node and transfer of a data packet D2 as a non-source network node in the communication network of FIG. FIG. 2 is a schematic diagram illustrating one embodiment of the method of the present invention implemented at a network node in the communication network of FIG. 1. FIG. 2 is a schematic diagram illustrating another embodiment of the method of the present invention, implemented in a network node in the communication network of FIG. 1.

  FIG. 1 shows an embodiment of a mesh type wireless packet switched ad hoc communication network (mesh network) according to the present invention. The mesh network includes a plurality of, here eight, for example, network nodes (Mesh Point) R, M1, M2,... M7, which have 14 physical point-to-point wireless data. The links L1, L2,... L14 are connected to each other in a mesh shape. For example, the root network node R is wirelessly connected to the third network node M3 via the first data link L1 in terms of data technology, and data is transmitted to the second network node M2 via the third data link L3. The wireless connection is technically wireless, and the wireless connection is data wirelessly connected to the first network node M1 via the sixth data link L6.

  Further, for example, the second network node M2 is data-technically connected to the third network node M3 via an eighth data link L8. All other provisions regarding data links and network nodes should be understood as well.

  In the mesh network of FIG. 1, a proactive routing tree is established from the root network node R, which is the root node, to all the network nodes M1, M2,... M7. The first data link L1, the third data link L3, the sixth data link L6, the second data link L2, the fourth data link L4, the fifth data link L5 and the seventh data link L7 are shown in FIG. In FIG. 1, it is indicated by a thick solid line, and other data links not belonging to the routing tree are indicated by thin broken lines.

  The establishment of the routing tree is performed on the basis of a standard mechanism using a distance vector and a link state protocol as provided by the routing protocol HWMP of the IEEE 802.11s standard, for example. Accordingly, the route network node R periodically transmits a routing inquiry message (RAN) to all the network nodes M1, M2,. This routing inquiry message (RAN) is used to specify the data transmission path to the root network node and update the routing table of the network nodes M1, M2,... M7. This establishes a unidirectional data transmission path for transmitting valid data packets from the network nodes M1, M2,... M7 to the root network node R, respectively. For example, a unidirectional data transmission path from the seventh network node M7 to the root network node R through the third network node M3 via the second data link L2 and the first data link L1 is proactive. Established. Further, for example, a unidirectional data transmission path from the fifth network node M5 to the root network node R through the second network node M2 via the fifth data link L5 and the third data link L3 is used. Established actively. All other proactively established unidirectional data transmission paths from the network nodes M1, M2... M7 to the root network node R should be understood similarly.

  In the network nodes M1, M2,... M7, the RWN response flag is set as the first flag. This RWN response flag can be set ("1") or cleared ("0").

  Further, in the network nodes M1, M2,... M7, the RWN transmitted flag is set as the second flag. This RWN transmitted flag can be set (“1”) or deleted (“0”).

  When the RWN response flag is set in the network nodes M1, M2,... M7 and the network node receives the RAN periodically transmitted from the root network node R, the network node responds with a response message (RWN). To the root network node R establishes a return path for transmitting (valid) data packets from the root network node R to the network node. The RWN response flag is set in the network nodes M1, M2,... M7, and the data transmission path from the network node to the root network node is detected by the network node, for example, by an error message indicating that the data link is lost. Even when the change is detected, the network node transmits a response message RWN to the root network node R, thereby establishing a return path for transmitting a (valid) data packet from the root network node R to the network node. The The RWN is, for example, a message provided in the routing protocol HWMP of the IEEE 802.11s standard, but is transmitted only before the start of data communication, that is, only before the transmission of the first data packet.

  In order to set or clear the RWN response flag in the network nodes M1, M2... M7, it is important that the upper layer in the wireless mesh network layer used for transmitting data packets between the network nodes in the communication network. To network nodes M1, M2,... M7 have received data packets, or the network node has only received data packets from another network node.

  This will be described in detail with reference to FIG. In FIG. 2, a data packet whose network node is a source network node is referred to as a data packet “D1”, and a data packet whose network node is not a source network node is referred to as a data packet “D2”. The data packet D1 comes from an upper layer (OSI model) such as an application, Internet protocol layer or IEEE 802.1D bridging, for example, within the mesh network as shown by the downward pointing arrow in FIG. 2 is used for data transmission and is transported in the wireless mesh layer indicated by S1 in FIG. 2 and then transmitted between network nodes. The upper layers are collectively indicated by S2 in FIG. In contrast, the data packet D2 is transmitted from one network node to another within the wireless mesh layer S1. Therefore, the same network node may be the source network node in the case of data packet D1 and not the source network node in the case of data packet D2. The target network node transfers the data packet D2 to one of the upper layers S2. This is not shown in detail in FIG. Only the network node that receives the data packet D1 from the higher layer S2 becomes the source network node, and sets and clears the RWN response flag. A network node that does not receive the data packet D1 from the higher layer S2 does not become a source network node and does not set or clear the RWN response flag.

  During initialization of the mesh wireless communication network, all RWN response flags of network nodes M1, M2,... M7 are cleared (as preset) (0). During initialization of the mesh type wireless communication network, all RWN transmitted flags of the network nodes M1, M2,... M7 are also cleared (as set in advance) (0).

  The root network node R periodically transmits the RAN to the mesh network, and each network node can input an appropriate data transmission path to the root network node R into the routing table of each network node after receiving the RAN. When the network node receives the RAN, the path metric to the target network node and the following metrics for the target network node (root network node) in the routing table (forwarding table) of the network node of the communication network that receives the RAN Add or update an entry containing a hop, ie, an entry containing a path metric to the target network node and the next network node on the path to the target network node. Furthermore, the hop count can be stored in the routing table. Such a method for establishing a routing tree is implemented on the basis of a procedure implemented in the hybrid routing protocol HWMP. Here, the routing inquiry message (RAN) is a proactive route request (PREQ) according to the hybrid routing protocol HWMP. Such steps are performed by all network nodes, whether or not they are source network nodes.

  In the following, it is assumed by way of example that the fifth network node M5 receives the data packet D1 from the upper layer S2 and functions as the source network node.

  When the fifth network node M5 receives the inquiry message RAN periodically transmitted from the root network node R, the fifth network node M5 transmits the data transmission path designated by the RAN to the fifth network node M5. The unidirectional data transmission path to the route network node R is periodically updated by inputting to the routing table or overwriting the conventional entry.

  At the time of inquiry for transmitting the data packet D1 to the root network node R, that is, before transmission of the first data packet of data communication, the fifth network node M5 generates a routing response message RWN to the routing network node R. Send. The root network node R receives this RWN, and inputs an appropriate data transmission path to the fifth network node M5 into the routing table of the fifth network node M5, whereby the root network node R A unidirectional data transmission path (return path) to M5 is established, and a bidirectional data transmission path is established between the root network node R and the fifth network node M5.

  All data packets transmitted from the fifth network node M5 after the last data packet D1 within a predetermined time period are considered as “subsequent” data packets. If the fifth network node M5 does not transmit the data packet D1 during the above period, all data packets transmitted next after this period have elapsed are considered as the “first” data packet. Different “data communication” is distinguished by such a settable period.

  Whether the data packet D1 is a “first” data packet or a subsequent data packet of the same data communication depending on the state of the RWN transmitted flag of the fifth network node M5. Can be detected. The RWN sent flag is set if the RWN was sent before the first data packet D1, or if the RWN was sent in response to the received RAN if the RWN response flag was set. . Each time a RAN is received that triggers transmission of the RWN when the RWN response flag is set, the RWN transmitted flag is cleared. That is, the off state / 0 is set.

  This further ensures that if the second RAN of the current route announcement is received (same sequence number or identifier), the RWN sent flag is not accidentally cleared and is based on the second RAN. It can also be ensured that no RWN is sent to the root network node. This is because the path metric of the second RAN is worse than the path metric of the first RAN. The RWN sent flag should not be reset at this point. This is because when reset, a further RWN is transmitted before the next data packet D1.

  It is advantageous to clear the RWN sent flag only if the RWN response flag is cleared. Thus, when the data packet D1 has to be transmitted between the RAN and the RWN belonging to the RAN, an additional RWN is not transmitted.

  When the RWN transmitted flag is erased in the fifth network node M5, the data packet D1 is regarded as the first data packet, whereas the RWN transmitted flag is set in the fifth network node M5. The data packet D1 is regarded as a subsequent data packet.

  In the first flag setting means of the method of the present invention, when the response message RWN is transmitted to the root network node R based on the first data packet D1, the RWN response flag of the fifth network node M5 is set.

  In the second flag setting means of the method of the present invention, which is more advantageous than the first flag setting means, the fifth network node is not used until the data packet D1 is transmitted from the fifth network node M5 to the root network node R. Set the M5 RWN response flag. The reason why the second flag setting means is more advantageous than the first flag setting means is that there is no other condition that needs to be inquired and the implementation is simple.

  When the fifth network node M5 receives the routing inquiry message RAN periodically transmitted from the root network node R, the fifth network node M5 moves the data transmission path designated by the RAN to the fifth network node M5. The data transmission path to the route network node R is updated by overwriting the existing entry in the routing table or overwriting the conventional entry. When the RWN response flag is set, the fifth network node M5 further transmits a response message RWN to the root network node R. The route network node R receives the RWN, and inputs the data transmission path to the fifth network node M5 designated by the RWN in the routing table of the route network node R or by overwriting the conventional entry. A unidirectional data transmission path (return path) from the root network node to the fifth network node M5 is established or updated, and bidirectional data is transmitted between the root network node and the fifth network node M5. A transmission path is established.

  The root network node R transmits a periodic inquiry message RAN to the network nodes M1, M2,. This means that each network node M1, M2,... M7 receives the same routing inquiry message a plurality of times, and each routing inquiry message indicates a different data transmission path to the root network node and possibly another path metric. Means to specify. Based on the identifier or sequence number, each network node M1, M2,... M7 can distinguish between different routing inquiry messages (RAN) transmitted periodically from the root network node R.

  When the fifth network node M5 receives the routing inquiry message RAN from the root network node R and the RWN response flag is set, the fifth network node M5 is in accordance with the first RWN transmission mode of the method of the present invention. In this case, the routing response message RWN can be immediately transmitted to the root network node R. If the fifth network node M5 receives another routing inquiry message RAN having the same sequence number or identifier from the root network node R, the fifth network node M5 again has a better path to the root network node R. A routing response message RWN is immediately sent to the root network node R for each RAN having metrics. This means that the routing response message RWN is sent from the fifth network node M5 to the root network node R until no routing inquiry message with better path metrics is received.

  If the fifth network node M5 receives the routing inquiry message RAN periodically transmitted from the root network node R and the RWN response flag is set, the fifth network node M5 is advantageous in the method of the present invention. According to the second RWN transmission mode, the routing response message RWN is transmitted to the root network node R for the first time after elapse of a selectable waiting time after receiving the RAN. All routing inquiry messages RAN (with the same sequence number or ID) received from the fifth network node M5 during such waiting time are analyzed in terms of path metrics, and the fifth network node M5 A routing response message RWN is sent to the root network node R for the RAN with the most advantageous path metrics. This reduces the probability that another RAN (with the same sequence number or ID) with better path metrics will be received from the fifth network node M5 after sending the routing response message RWN, advantageously The number of routing response messages RWN transmitted can be reduced, and the amount of data generated can be reduced.

  Also, when the data transmission path from the fifth network node M5 to the root network node R changes for a reason different from the reception of the RAN and the RWN response flag is set, the routing response message RWN is sent to the fifth network. It can be generated by the node M5 and transmitted to the root network node R. This may be the case, for example, when the fifth network node M5 receives an error message signifying a missing data link in the data transmission path or via a hardware detector detecting a missing neighboring data link. The case is true.

  There are various reset means for erasing the RWN response flag.

  According to the first flag reset means, the RWN response flag is reset to 0 by the fifth network node M5 immediately after the RWN is transmitted as a response to the reception of the RAN. If the fifth network node M5 does not transmit the data packet D1 within the time interval for the root network node R to periodically transmit the RAN, the RWN does not respond to the received RAN. Each time a data packet D1 is transmitted during this time interval, the RWN response flag is set again.

  According to the second flag resetting means, the RWN response flag is set to 0 by the fifth network node M5 before the first data packet D1 after elapse of a selectable period after the RWN is transmitted as a response to the reception of the RAN. Or reset to 0 by the fifth network node M5 before the data transmission path is changed. At that time, each time the data packet D1 is transmitted from the fifth network node M5 to the root network node R, a timer for measuring the lapse of a selectable period is reset to the start value. In that case, in order to reach the fifth network node M5 when the RWN response flag is set in the first place, the timeout start value is set so that the root network node R periodically transmits the RAN. Must be greater than the time interval.

  The first flag reset means corresponds to the routing protocol order, while the second flag reset means corresponds to data traffic. The advantage of the first flag reset means is that no additional timer is required. The advantage of the second flag reset means is that it can be implemented very easily.

  If the fifth network node M5 does not transmit the data packet D1 within the time interval for the root network node R to periodically transmit the RAN, the RWN does not respond to the received RAN. The RWN response flag is set again for each data packet D1 transmitted during this time interval.

  The RWN parameter transmitted from the fifth network node M5 to the root network node R is set according to HWMP rules or according to RM-AODV / AODV which is the basis of HWMP. The lifetime in the RWN is set to the lifetime included in the RAN or proactive RREQ.

  Reference is now made to FIG. This figure is a schematic diagram for explaining an embodiment of the method of the present invention implemented in the communication network of FIG. 1, in which the first flag reset means is implemented to reset (erase) the RWN response flag. To do.

  In FIG. 3, the line “FL” represents the state of the RWN response flag that can be erased (0) or set (1). Line M5 represents a fifth network node M5 that functions as a source network node. The arrow hitting the line M5 indicates a data packet received by the fifth network node M5. The arrow starting from line M5 indicates a data packet transmitted by the fifth network node M5. In FIG. 3, each of the lines FL or M5 extends downward from above. This represents the time course. The letters A to L represent different situations during the implementation of the method for establishing a bidirectional data transmission path between the fifth network node M5 and the root network node R.

  In FIG. 3, the RWN transmitted flag of the fifth network node M5 is not shown. In the presetting, the RWN response flag and the RWN transmitted flag of the fifth network node M5 are deleted.

  In the situation “A”, the fifth network node M5 receives the routing inquiry message RAN from the root network node R, and the data transmission path specified in the routing inquiry message RAN is transferred to the routing table of the fifth network node M5. Or update the corresponding entry in the routing table to establish a unidirectional data transmission path from the fifth network node M5 to the root network node R, and the fifth network node M5 Updates the RAN and forwards this modified RAN to the next network node with a slight time delay. The RWN response flag of the fifth network node M5 is still erased. The RWN transmitted flag of the fifth network node M5 is still erased.

  In situation "B", the fifth network node M5 receives the data packet D2 from another network node, for example from the second network node M2, and forwards this data packet D2 to another network node. The RWN response flag of the fifth network node M5 is still erased. The RWN transmitted flag of the fifth network node M5 is still erased.

  In situation “C”, the fifth network node M5 again receives the data packet D2 from another network node, for example from the second network node M2, and forwards this data packet D2 to another network node. The RWN response flag of the fifth network node M5 is still erased. The RWN transmitted flag of the fifth network node M5 is still erased.

  In situation "D", the fifth network node M5 receives another (newly generated) inquiry message RAN from the root network node R having a different sequence number from the preceding RAN, and the fifth network node By updating the corresponding entry in the routing table of M5, an updated unidirectional data transmission path from the fifth network node M5 to the root network node R is established, and the fifth network node M5 is connected to the RAN. And this modified RAN is forwarded to the next network node with a slight time delay. The RWN response flag of the fifth network node M5 is still erased. The RWN transmitted flag of the fifth network node M5 is still erased.

  In situation “E”, the fifth network node M5 receives the data packet D1 from the upper layer (S2). That is, the fifth network node M5 receives a data packet to be transmitted to the root network node R from a layer higher than the wireless mesh layer of the mesh network exchanged by the network node. This is not shown in detail in FIG.

  Before sending the data packet D1 to the root network node R, that is, before sending the first data packet D1, the fifth network node M5 generates a response message RWN and sends it to the routing network node R. The root network node R receives this RWN, and inputs an appropriate data transmission path to the fifth network node M5 into the routing table of the fifth network node M5, whereby the root network node R A unidirectional data transmission path (return path) to M5 is established, and a bidirectional data transmission path is established between the fifth network node M5 and the root network node R. At the same time, the fifth network node M5 sets the RWN transmitted flag of the fifth network node M5. Next, the fifth network node M5 transmits the data packet D1 to the root network node R. At the same time, the fifth network node M5 sets the RWN response flag of the fifth network node M5.

  In situation “F”, the fifth network node M5 receives another data packet D1 and transmits the data packet D1 to the root network node R. This data packet D1 is not shown in detail in FIG. The RWN response flag of the fifth network node M5 is still set. The RWN transmitted flag of the fifth network node M5 is still set.

  In situation “G”, the fifth network node M5 receives another data packet D1 and transmits the data packet D1 to the root network node R. This data packet D1 is not shown in detail in FIG. The RWN response flag of the fifth network node M5 is still set. The RWN transmitted flag of the fifth network node M5 is still set.

  In the situation “H”, the fifth network node M5 receives another data packet D1 and transmits the data packet D1 to the root network node R. This data packet D1 is not shown in detail in FIG. The RWN response flag of the fifth network node M5 is still set. The RWN transmitted flag of the fifth network node M5 is still set.

  The fifth network node M5 then receives another (newly generated) routing inquiry message RAN from the root network node R having a sequence number different from that of the preceding RAN in the situation “H”. By updating the corresponding entry in the routing table of the network node M5, an updated unidirectional data transmission path from the fifth network node M5 to the root network node R is established, and the fifth network node M5 updates the RAN and forwards this modified RAN to the next network node with a slight time delay. Furthermore, the fifth network node M5 clears or keeps the RWN transmitted flag of the fifth network node M5. This is because the RWN response flag of the fifth network node M5 is set.

  Since the fifth network node M5 receives the response message RAN periodically transmitted from the root network node R and the RWN response flag is set, the fifth network node M5 generates the response message RWN, for example, Transmit to the root network node R with a slight time delay. The fifth network node M5 sets the RWN transmitted flag of the fifth network node M5. The root network node R receives the RWN and overwrites the corresponding data transmission path from the root network node R to the fifth network node M5 by overwriting the corresponding data transmission path to the fifth network node M5 in the routing table of the root network node R. The unidirectional data transmission path (return path) up to is updated.

  Due to the time delay from when the RAN is received until the RWN is sent to the root network node R, another RAN (with the same sequence number) with better path metrics may receive a fifth after sending the routing response message RWN. The probability of being received by the network node M5 is reduced and the number of RWNs transmitted to the root network node R is reduced.

  According to the first flag reset means for resetting the RWN response flag, the RWN response flag is cleared together with the transmission of the response message RWN.

  In situation “I”, the fifth network node M5 receives another data packet D1 determined for the root network node R and transmits the data packet D1 to the root network node R. This data packet D1 is not shown in detail in FIG. The RWN response flag of the fifth network node M5 is set. The RWN transmitted flag of the fifth network node M5 is still set.

  In situation “J”, the fifth network node M5 receives another data packet D1 and transmits the data packet D1 to the root network node R. This data packet D1 is not shown in detail in FIG. The RWN response flag of the fifth network node M5 is left set. The RWN transmitted flag of the fifth network node M5 is still set.

  In situation “K”, the fifth network node M5 receives from the root network node R another (newly generated) inquiry message RAN having a different sequence number than the preceding RAN, and the fifth network node By updating the corresponding entry in the routing table of M5, an updated unidirectional data transmission path from the fifth network node M5 to the root network node R is established, and the fifth network node M5 is connected to the RAN. And this modified RAN is forwarded to the next network node with a slight time delay, for example. Furthermore, the fifth network node M5 clears or keeps the RWN transmitted flag of the fifth network node M5. This is because the RWN response flag of the fifth network node M5 is set. Since the fifth network node M5 receives the routing inquiry message RAN periodically transmitted from the root network node R and the RWN response flag is set, the fifth network node M5 generates the routing response message RWN. For example, the RWN is transmitted to the root network node R with a slight time delay. The root network node R receives the RWN and overwrites the corresponding data transmission path from the root network node R to the fifth network node M5 by overwriting the corresponding data transmission path to the fifth network node M5 in the routing table of the root network node R. The unidirectional data transmission path (return path) up to is updated. Furthermore, according to the first flag resetting means for resetting the RWN response flag, the RWN response flag is cleared together with the transmission of the response message RWN. The RWN transmission completion flag is set together with the transmission of the RWN.

  In the situation “L”, the fifth network node M5 receives another (newly generated) routing inquiry message RAN having a different sequence number from the previous RAN from the root network node R, and the fifth network node By updating the corresponding entry in the routing table of M5, an updated unidirectional data transmission path from the fifth network node M5 to the root network node R is established, and the fifth network node M5 is connected to the RAN. And this modified RAN is forwarded to the next network node with a slight time delay. The fifth network node M5 receives the response message RAN periodically transmitted from the root network node R. However, since the RWN response flag is cleared, the fifth network node M5 does not generate the response message RWN. The corresponding RWN is not transmitted to the root network node R. The RWN transmitted flag is deleted upon receipt of the RAN.

  Reference is now made to FIG. In the figure, another embodiment of the method of the present invention implemented in the communication network of FIG. 1 is schematically illustrated, in which a second flag resetting means is implemented to reset the RWN response flag.

  In FIG. 4, as in FIG. 3, the line “FL” represents the state of the RWN response flag, and the line M5 represents the fifth network node M5. Furthermore, the time course of the count timer TI for resetting the RWN response flag of the fifth network node M5 is shown. The timer TI counts from a start time t to an elapsed time 0 when a settable time t has elapsed. In the first place, the start value of the timeout must be larger than the time interval for the root network node R to transmit the RAN periodically so that the RAN reaches the fifth network node M5 when the RWN response flag is set. I must. The letters A to L represent different situations during the implementation of the method for establishing a bidirectional data transmission path between the fifth network node M5 and the root network node R.

  In FIG. 4, the RWN transmitted flag of the fifth network node M5 is not shown. In the second flag reset means for resetting the RWN response flag, whether the data packet D1 is the first data packet (whether the RWN response flag is cleared) or another data packet (whether the RWN response flag is RWN response flag can be used instead of the RWN sent flag to detect whether it is set. In the presetting, the RWN response flag of the fifth network node M5 is deleted. In the presetting, the RWN transmitted flag of the fifth network node M5 is deleted.

  In the situation “A”, the fifth network node M5 receives the inquiry message RAN from the root network node R, and transfers the data transmission path specified in the inquiry message RAN to the routing table of the fifth network node M5. Or by updating the corresponding entry in the routing table, a unidirectional data transmission path from the fifth network node M5 to the root network node R is established, and the fifth network node M5 is connected to the RAN. And this modified RAN is forwarded to the next network node with a slight time delay. The RWN response flag of the fifth network node M5 is still erased. The RWN transmitted flag of the fifth network node M5 is still erased.

  In situation "B", the fifth network node M5 receives the data packet D2 from another network node, for example from the second network node M2, and forwards this data packet D2 to another network node. The RWN response flag of the fifth network node M5 is still erased. The RWN transmitted flag of the fifth network node M5 is still erased.

  In situation “C”, the fifth network node M5 again receives the data packet D2 from another network node, for example from the second network node M2, and forwards this data packet D2 to another network node. The RWN response flag of the fifth network node M5 is still erased. The RWN transmitted flag of the fifth network node M5 is still erased.

  In situation "D", the fifth network node M5 receives another (newly generated) inquiry message RAN from the root network node R having a different sequence number from the preceding RAN, and the fifth network node By updating the corresponding entry in the routing table of M5, an updated unidirectional data transmission path from the fifth network node M5 to the root network node R is established, and the fifth network node M5 is connected to the RAN. And this modified RAN is forwarded to the next network node with a slight time delay, for example. The RWN response flag of the fifth network node M5 is still erased. The RWN transmitted flag of the fifth network node M5 is still erased.

  In situation “E”, the fifth network node M5 receives the data packet D1 from the upper layer (S2). That is, the fifth network node M5 receives a data packet to be transmitted to the root network node R from a layer higher than the wireless mesh layer of the mesh network exchanged by the network node. This is not shown in detail in FIG.

  Before sending the data packet D1 to the root network node R, ie before sending the first data packet D1, the fifth network node M5 generates a response message RWN and sends it to the routing network node R. The root network node R receives this RWN, and inputs an appropriate data transmission path to the fifth network node M5 into the routing table of the fifth network node M5, whereby the root network node R A unidirectional data transmission path (return path) to M5 is established, and a bidirectional data transmission path is established between the fifth network node M5 and the root network node R. At the same time, the fifth network node M5 sets the RWN transmitted flag of the fifth network node M5. Next, the fifth network node M5 transmits the data packet D1 to the root network node R, sets the RWN response flag of the fifth network node M5, and starts the timer TI at the start time t.

  In situation “F”, the fifth network node M5 receives another data packet D1 and transmits the data packet D1 to the root network node R. This data packet D1 is not shown in detail in FIG. The RWN response flag of the fifth network node M5 is still set. The RWN transmitted flag of the fifth network node M5 is still set. The timer TI is reset and restarted at the start time t.

  In situation “G”, the fifth network node M5 receives another data packet D1 and transmits the data packet D1 to the root network node R. This data packet D1 is not shown in detail in FIG. The RWN response flag of the fifth network node M5 is still set. The RWN transmitted flag of the fifth network node M5 is still set. The timer TI is reset and restarted at the start time t.

  In the situation “H”, the fifth network node M5 receives another data packet D1 and transmits the data packet D1 to the root network node R. This data packet D1 is not shown in detail in FIG. The RWN response flag of the fifth network node M5 is still set. The RWN transmitted flag of the fifth network node M5 is still set. The timer TI is reset and restarted at the start time t.

  Next, the fifth network node M5 receives another (newly generated) routing inquiry message RAN having a sequence number different from that of the preceding RAN from the root network node R, and the routing of the fifth network node M5. By updating the corresponding entry in the table, an updated unidirectional data transmission path from the fifth network node M5 to the root network node R is established, and the fifth network node M5 updates the RAN. This modified RAN is transferred to the next network node with a slight time delay. The fifth network node M5 clears the RWN transmitted flag of the fifth network node M5 or keeps it set. This is because the response flag of the fifth network node M5 is set.

  Since the fifth network node M5 receives the routing inquiry message RAN periodically transmitted from the root network node R and the RWN response flag is set, the fifth network node M5 generates the routing response message RWN. For example, the RWN is transmitted to the root network node R with a slight time delay. The fifth network node M5 sets the RWN transmitted flag of the fifth network node M5. The root network node R receives the RWN and overwrites the corresponding data transmission path from the root network node R to the fifth network node M5 by overwriting the corresponding data transmission path to the fifth network node M5 in the routing table of the root network node R. The data transmission path (return path) up to is updated. According to the second flag reset means for resetting the RWN response flag, the RWN response flag is still set.

  In situation “I”, the fifth network node M5 receives another data packet D1 and transmits the data packet D1 to the root network node R. This data packet D1 is not shown in detail in FIG. The RWN response flag of the fifth network node M5 is still set. The RWN transmitted flag of the fifth network node M5 is still set. The timer TI is reset and restarted at the start time t.

  In situation “J”, the fifth network node M5 receives another data packet D1 and transmits the data packet D1 to the root network node R. This data packet D1 is not shown in detail in FIG. The RWN response flag of the fifth network node M5 is left set. The RWN transmitted flag of the fifth network node M5 is still set. The timer TI is reset and restarted at the start time t.

  In situation “K”, the fifth network node M5 receives from the root network node R another (newly generated) routing inquiry message RAN having a different sequence number than the preceding RAN, and By updating the corresponding entry in the routing table of the node M5, an updated unidirectional data transmission path from the fifth network node M5 to the root network node R is established, and the fifth network node M5 Update the RAN and forward this modified RAN to the next network node with a slight time delay, for example. Further, the fifth network node M5 clears the RWN transmitted flag of the fifth network node M5 or keeps it set. This is because the RWN response flag of the fifth network node M5 is set. Since the fifth network node M5 receives the inquiry message RAN periodically transmitted from the root network node R and the RWN response flag is set to “1”, the fifth network node M5 transmits the routing response message RWN. For example, the RWN is transmitted to the root network node R with a slight time delay. The root network node R receives the RWN and overwrites the corresponding data transmission path from the root network node R to the fifth network node M5 by overwriting the corresponding data transmission path to the fifth network node M5 in the routing table of the root network node R. The data transmission path (return path) up to is updated. According to the second flag reset means for resetting the RWN response flag, the RWN response flag is still set. The RWN transmitted flag is set.

  In the situation “L”, the time of the timer TI has elapsed, and the RWN response flag of the fifth network node M5 is cleared. Next, the fifth network node M5 receives another (newly generated) routing inquiry message RAN having a sequence number different from that of the preceding RAN from the root network node R, and the routing of the fifth network node M5. By updating the corresponding entry in the table, an updated unidirectional data transmission path from the fifth network node M5 to the root network node R is established, and the fifth network node M5 updates the RAN. The modified RAN is transferred to the next network node with a slight time delay, for example. The fifth network node M5 receives the routing response message RAN periodically transmitted from the root network node R, but the RWN response flag is cleared, so that the fifth network node M5 generates the response message RWN. Therefore, the corresponding RWN is not transmitted to the root network node R. The RWN transmitted flag is deleted.

  In the following, based on one calculation example, a conventional method (Comparative Example 1) for transmitting a routing response message to the root network node only once before the first data packet D1 and a routing inquiry message (RAN) are received. The advantages of the method of the present invention (Example 1) over another possible approach (Comparative Example 2), which always sends a routing response message to the root network node later.

Use the following abbreviations:
N = number of network nodes H = path length between network node and root network node dH = average path length from all network nodes to root network node; dH ≧ 1
t_g = t_gesamt: considered time interval t_d = t_daten: time for network node to send data to root network node as source network node RAI = duration of routing response message (RAN) interval ara = during the considered time interval Number of routing inquiry messages (RAN) initiated by the root network node at ara = ((t_g / RAI) +1)

Example 1
In example 1, in a proactive RAN with a reactive (on-demand) RWN, the number of RANs is ara * N.
Number of RWNs: ((t_d / RAI) +1) * H
Total number of routing messages:
ara * N * ((t_d / RAI) +1) * H

Comparative Example 1
Number of RAN: ara * N
Number of RWNs: H (before the first data packet D1)
Total number of routing messages: ara * N + H

Comparative Example 2
Number of RAN: ara * N
Number of RWNs: ara * N * dH
Total number of routing messages: ara * N + (1 + dH)

Typical values for N, H, dH, t_g, t_d and RAI are, for example:
N = 30
H = 4
dH = 3
t_g = 900 seconds t_d = 300 seconds RAI = 5 seconds.

In such a case, the cost (total number of routing messages sent) is as follows: (ara = 181)
Number of routing messages in example 1: 5675
Number of routing messages in Comparative Example 1: 5431
Number of routing messages in comparative example 2: 21720

  As this calculation example shows, the number of routing messages can be significantly reduced by Example 1 (the method according to the invention), here it can be reduced by 73.9%.

The following are other features of the present invention:
The general idea of the present invention to improve the no registration mode is:
The network node responds to the RAN with an RWN only if the network node sends a data packet D1 to the root network node and the network node is the source network node of the data packet D1;
RWN response flag that determines whether or not to transmit RWN as a response to RAN, OFF state / 0 means not to transmit RWN, ON state / 1 responds when RAN is received An RWN response flag which means to send the RWN to the root network node as
And various mechanisms for setting and clearing the above flags.

These basic rules are:
[RWN response flag = on state / 1] and [[network node received RAN] or [route to route network node changed]]
When the above condition is satisfied, the RWN is transmitted from the network node to the root network node.

  The mechanism of the method according to the invention is only implemented by the network node that is the source network node of the data packet D1 and is sent to the root network node R. That is, the data packet arrives at this network node from an upper layer, and this network node is the first node of this mesh connection. An intermediate node that receives the data packet D2 and forwards it to another network node according to the routing table need not consider the mechanism defined in the method of the present invention for this data packet D2. In particular, the RWN is not transmitted to the root network node based on the data packet D2, and the RWN response flag is not set. When data is exchanged between the network node and the root network node according to the method of the present invention, the forward path and the return path for transmitting data packets between the network node and the root network node are the same. You can go through network nodes. The outbound route and the return route are routed through the best route. By the method according to the present invention, it is possible to eliminate the loss of data link (link collapse) in both the forward and return paths. It is not necessary to eliminate the lack of data links on the return path from the root network node to the network node by a relatively troublesome AODV route recovery mechanism.

  With the RWN response flag as described above, it is possible to easily determine whether or not to transmit the RWN as a response to the RAN. A flexible configuration can be realized by various methods for resetting the RWN response flag, for example, the RWN is still transmitted and the return time from the root network node to the network node is still maintained in the last data packet. Can be used after. By responding to the RAN with the RWN, the change in the data transmission path in the intermediate node in the return path direction can be updated. Even if the data transmission path from the network node to the root network node changes due to a reason different from the reception of the RAN, an additional improvement of transmitting the RWN to the root network node when the RWN response flag is set, It is also possible to transfer the change of the outward route to the return route and update the return route accordingly. By using the lifetime of RAN or proactive RREQ as the lifetime in the transmitted RWN, the forward path and the return path can be provided with equal length.

Claims (18)

A method for establishing a bidirectional data transmission path in a mesh type wireless packet switching communication network having a plurality of network nodes, comprising:
One of the network nodes functions as a root network node;
In the mesh type wireless packet switching communication network,
In order to proactively establish a logical topology in the form of at least one routing tree, the root network node (R) of the routing tree has an initial unidirectional data transmission path to the root network node (R). A routing inquiry message (RAN) to be specified is transmitted to the network nodes (M1 to M7) of the mesh type wireless packet switching communication network at periodic time intervals,
Each of the network nodes (M1 to M7) of the routing tree is provided with a first flag that can be shifted to two different states in order to control transmission of a routing response message (RWN),
When the first flag is in a selectable first state (ON), when the network node (M5) receives the routing inquiry message (RAN), the second unidirectional to the network node By transmitting a routing response message designating the data transmission path of the root network node (R) to the root network node (R), a bidirectional data transmission path is established between the root network node (R) and the network node (M5). And
A method wherein the network node does not send a routing response message if the first flag is in the second state.   Data packet (M5) for transmission to the root network node (R) as the first network node of the mesh type wireless packet switching communication network on the data transmission path to the root network node (R) The method according to claim 1, wherein if D1) is received, the first flag of the network node (M5) is shifted to the first state (ON).   The first flag of the network node (M5) is shifted to the second state (OFF) immediately after the routing response message (RWN) is transmitted to the root network node (R). the method of. The data packet (D1) received by the network node (M5) as the first network node of the mesh type wireless packet switching communication network on the data transmission path to the root network node (R) is sent to the root network node (R). After the elapse of a selectable first period started simultaneously with transmission, the first flag of the network node (M5) is shifted to the second state (OFF);
The method according to any one of claims 1 to 3, wherein each time the data packet (D1) is transmitted, the first period is reset to a selectable starting value for the first time.   This is a case where the network node receives a data packet (D1) to be transmitted to the root network node as the first network node of the mesh type wireless packet switching communication network on the data transmission path to the root network node. Then, over the second period immediately before the reception of the data packet, the data is transmitted to the root network node as the first network node of the mesh type wireless packet switching communication network on the data transmission path to the root network node (R). The network node (M5) sends a routing response message (RWN) to the root network node (R) if it does not receive a data packet (D1) to do so. The method described.   When the second flag that is provided in the network node to control the transmission of the routing response message and can be shifted to two different states (ON / OFF) is shifted to the selectable first state (0) The method of claim 5, wherein the network node (M5) transmits a routing response message (RWN) to the root network node (R).   The method according to claim 6, wherein a second flag of the network node (M1 to M7) is set to the second state (OFF) at the initial initialization of the mesh type wireless packet switched communication network.   When the network node transmits a routing response message (RWN) to the root network node (R) before the first data packet (D1) of data communication, the first flag of the network node (M5) is set to the first flag. The method according to any one of claims 1 to 7, wherein the state (ON) is entered.   The method according to any one of claims 1 to 8, wherein the routing response message (RWN) is sent immediately after the routing inquiry message (RAN) is received at the route network node (R).   The method according to any one of claims 1 to 8, wherein after said routing inquiry message (RAN) is received at said route network node (R), said routing response message (RWN) is transmitted with a time delay. .   The first flag of the network node (M1 to M7) is set to the second state (OFF) at the first initialization of the mesh type wireless packet switching communication network. The method according to claim 1.   The lifetime parameter of the routing response message (RWN) that indicates the lifetime of the second unidirectional data transmission path to the network node is included in the received routing inquiry message (RAN) as follows: 12. The method according to claim 1, wherein the lifetime parameter of the first unidirectional data transmission path to the root network node (R) is set to a lifetime parameter that is indicated by a sign.   13. A method according to any one of claims 1 to 12, based on the hybrid routing protocol HWMP. 14. A method according to any one of claims 1 to 13, in particular for establishing a bidirectional data transmission path in a mesh radio packet switched communication network having a plurality of network nodes,
One of the network nodes functions as a root network node;
In the mesh type wireless packet switching communication network,
In order to proactively establish a logical topology in the form of at least one routing tree, the root network node (R) of the routing tree has an initial unidirectional data transmission path to the root network node (R). A routing inquiry message (RAN) to be specified is transmitted to the network nodes (M1 to M7) of the mesh type wireless packet switching communication network at periodic time intervals,
Each of the network nodes (M1 to M7) of the routing tree is provided with a first flag that can be shifted to two different states in order to control transmission of a routing response message (RWN),
If the first flag is in a selectable first state (ON), the network is detected when a change in the first unidirectional data transmission path to the root network node (R) is detected. The node (M5) transmits a routing response message designating a second unidirectional data transmission path to the network node to the root network node (R), whereby the root network node (R) and the network A bidirectional data transmission path is established with the node (M5),
A method wherein the network node does not send a routing response message if the first flag is in the second state.   15. A mesh type wireless packet switched communication network, wherein the network nodes (M1 to M7) are adapted to carry out the method according to any one of claims 1-14. Machine-readable program code for a network node (M1-M7) of a mesh type wireless packet switched communication network according to claim 15,
Machine-readable program code comprising control instructions for said network node to perform the method according to any of claims 1-14.   The network nodes (M1-M7) of the mesh type wireless packet switched communication network according to claim 15, wherein the machine readable program code according to claim 16 is executed.   A storage medium in which the machine-readable program code according to claim 16 is stored.

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